The objective of this study is to analyze the neural organization of central cardiovascular pathways. The first part deals with the organization of descending catecholamine and medullary pathways which project to the sympathetic preganglionic outflow. The objective is to characterize those systems which project to the intermediolateral cell column. In addition, their ascending projections will also be studied. The second objective is to characterize the inputs to the nucleus of the solitary tract, an area known to be involved in blood pressure control. The third objective is to study the descending projections from cardiovascular areas of the hypothalamus. The fourth objective is to analyze the A5 catecholamine pressor response using electrical stimulation and anatomical techniques and to determine whether the critical element involves a direct projection to the spinal cord or some other pathway.